Sleeping in the Nesting Box?

My 4 chicks, 7-8 weeks old, are now finally out in the coop. I have roosts for them, two that are kitty-corner 1 foot off the ground and one that spans the width 2 feet off the ground. They don't seem to want to use them to sleep though. They keep huddling up in the nesting boxes when going to sleep at night. I've placed them on the roosts to let them now that hey look these things are here, but they just don't want to use them. Are they just too young to use them yet maybe? Or should I bar off the nesting boxes until they are of laying age? Oh and the temp here at night is in the upper 30's to mid 40's if that makes any difference. Any ideas? Thanks

young chicks like that do not usually roost at night, so it will take time before they start using them. if you do not want them soiling the nesting boxes you could block them off until they get close to laying age.